"Star Trek" icon William Shatner is returning to one of his favorite genres with the new sci-fi film "Escape from Planet Earth," but this time around, he wanted to make sure it was safe to take some special passengers alongfor the ride.

In a recent interview, Shatner, 81, told me that it was important to him to make a movie that he and his wife and three grandchildren -- two are age 7 and the other is 10 -- could see without worry. And that's not easy given the few number of films made for families in theaters.

"The line between having a film that's entertaining between a 6-year-old and a 12-year-old is very narrow, and the reaction we're getting with this movie is that we've been able place it exactly in the middle of that line -- where you don't scare a 6 year-old and yet you occupy a 12-year-old's attention," Shatner explained.

Shatner voices the pivotal role of General Shanker in "Escape from Planet Earth," a military heavy who lures the smartest aliens from across the galaxy to earth so he can imprison them, steal their technology, and make loads of cash off it. Shanker's operation however, is threatened when he captures Scorch Supernova (Brendan Fraser) -- a national hero among his blue alien population -- and his brainy brother, Gary (Rob Corddry), comes to rescue him.

Opening in 2D and 3D in theaters nationwide on Friday, "Escape from Planet Earth" also stars the voices of Sofia Vergara, Jessica Alba, Ricky Gervais, George Lopez and Sarah Jessica Parker.

While Shatner plays the "bad guy" in "Escape from Planet Earth," he wants to point out that evil here is "evil fun," and not "evil evil." Evil fun, he said, helps the younger audience members retain their naiveté and avoids what true evil is.

"You have to be careful, because a 6-year-old doesn't know what evil is," Shatner said. "My daughters, for example, are very careful about what they let their children see. I guess you can make an argument either way. You can let them retain their innocence as long as possible, or you can say, 'There are evils in the world.' But at what point do you do that? I don't have the answers to that."

Shatner, of course, has one of the most distinct voices in the entertainment business, and part of the allure of voicing a character for an animated film like "Escape from Planet Earth" is that he can have creative input into shaping the character.

In this case, General Shanker is a threatening-looking character, but the voice coming out of him isn't exactly what you would expect.

"They drew a large, imposing figure, but I wanted to move in the opposite direction," Shatner recalled. "So I chose to do a little lisp, and I chose to make him more diddly and more feral, so he's more of a wild cat than a wild lion."

Of course, Shatner has been deeply connected to the space and sci-fi genre for years, dating back to the "Star Trek" television series and movies, and in more recent years, though his "Star Trek" novels.

Still, the prolific actor and author said it's fun to do a film like "Escape from Planet Earth" with alien characters involved, because it once again gives him the chance to contemplate the boundless universe that we live in -- a universe he says undoubtedly contains other life forms.

To believe otherwise, Shatner said, is "ludicrous."

"The stuff that I am starting to think about it is, the universe is so complex, that we can't even begin to imagine what we don't know," Shatner observed. "We mere mortals don't have the ability to encompass what strange things are out there that are bigger than our imagination. We have no possibility of finding out what it is, because we can't imagine what is out there."

Shatner added while scientists have caught glimpses of how the universe works, our knowledge of it is still meager.

"Even with our total knowledge, we still know nothing," Shatner said. "So with that point of view, to think we're the only ones is the universe, in this complex, multi-layered -- no English word can contain what strange things are out there. How dare we say, 'Well, we're the only ones out there.'"

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